Means for roll-threading and pointing screws



June 6, 1933. P. L. ROBERTSON 1,913,143

MEANS FOR ROLL THREADING AND POINTING SCREWS Filed Feb. 24, 1951 AAAAAAAAA Patented June 6, 1933 UNITED STATES PETER L. ROBERTSON, OF MILTON, ONTARIO, CANADA.

. MEANS FOR ROLL-THREADING AN D POINTING SCREWS Application filed February 24, 1931.

The principal objects of this invention are to efiect a material saving in the cost of producing machine threaded screws with tapered ends, and to provide a simple and inexpensive means for accomplishing the threading and tapering of the end of the screw in a single operation.

The principal feature of the invention con sists in the novel construction and arrangement of a swaging tool within a thread rolling die block, whereby the metal of the end of the screw blank is swaged longitudinally to form a taper end during the operationof rolling the thread.

In the drawing, Figure 1 is a perspective view of a portion of a screw thread rolling machine showing the position of the rolling dies fitted with the swaging tool for form ing the tapered end. i y Figure 2 is an enlarged elevational view of the die block and point swaging tool showing screws arranged in several positions therealong illustrating the progressive swaging operation.

Figure 3 is an end elevational view showing the thread rolling dies and the relative positions of the screw and the swaging tool.

Figures 4:, 5 and 6 are cross sectional views through the swaging tool taken in several of the positions illustrating the operation shown in Figure 2.

Figure 7 is a perspective view of the swaging tool removed from thedie block.

Manufacturers of machinery of various kinds have for a considerable period realized the advantages of the use of bolts and screws made with rolled threads and such screws are coming into an increasingly (greater de mand. It has also been recognize that much time may be saved in the assembling of parts by the use of screws with a pointed or tapered end to facilitate the placing of the screw properly and quickly in the threaded hole.

The tapering of the points of machine screws has heretofore required a special operation which is expensive and therefore adds greatly to the cost of the screws.

The present invention has been devised to perform the rolling of the thread and the tapering of the screw end in the one opera- Serial No. 517,986.

tion and this has been accomplished in a remarkably simple manner by inserting into the thread rolling die a tool which will cold forge or swage the metal of the end of the blank to a taper end.

In the drawing shown herewith the die block 1 which co-operates with the die block 2 carried by the reciprocating member of the thread rolling machine, has a slot 3'cut longitudinally thereof parallel with the top 30 edge t.

Within the slot 3 is placed a hardened steel tool 5 formed of a narrow strip of metal having its outer face formed with an angular ridge 6 which extends diagonally from end to end of the tool and the commencement end 7 of the ridge is arranged close to the upper side of the slot 3 and is only slightly higher than the thread cutting edges 8 of the rolling die. It will be noted that the ridge 6 is not parallel to the direction of reciprocation of the die or to the path of movement of the blank as it is advanced between the dies, but is angularly or diagonally related thereto so that a very valuable swedging and upsetting action is produced, to be later defined herein.

The edgeof the ridge 6 is adapted to imbed itself in the metal of the blank immediatelyadjacent to the lower end of the thread of the screw and as the rolling of the screw progresses the angular or diagonal slant of the ridge swages the metal endwise as is very clearly illustrated in Figures 2 to 6. I

It will be noted, particularly on reference to Figure 2 that the swaging edge of the ridge 6 rises progressively from the die surface, that is to say, while the commencement end 7 is only slightly higher than the thread rolling ridges 8 the oppositeend 9 is raised considerably above them. The diagonal and gradually rising cutting edge progressively forces the metal of the blank endwise and continues to out further in toward the axis of rotation of the screw as it progresses in its movement between the thread rolling dies. This action continues until finally the ridge edge passes in its diagonal'direction beyond the end of the blank, or correctly stating, the screw in its progressive movement moves clear of the edge of the ridge, as shown at the point X in igures 2 and 6. "his is entirely a swedgin or dis lacing action so that the metal 0 the ot erwise abrupt or squared end of the blank is gathered by the ridge as the latter retreats longitudinall of the blank and pushed downwardly y the ridge which progressively advances above the working surface of the die closer to the axis of the lank so that a conical extension or point is actually built onto the screw end composed mainly or entirely of displaced metal.

The bevelled surface 10 on the side of the ridge adjacent the screw continues to engage the tapered swaged end of the screw and a further rolling action continues to shape the metal of the point of the screw to a sharper apex. It is not necessary that this action be continued until a sharp point be formed on the screw and the roll swedging action is continued only long enough to smooth the' metal down to a uniform surface following the swedging and pushing action of the tool ed e 6.

i will be further noted thatthe extension thus built onto the end of the screw from metal of the blank is actually of a hollow or shell like nature so that the minimum of metal is required to produce a given length of screw, there is no waste, and the formation being produced in a gradual and progressive manner, eliminates excessive or peak strains on the working members.

It will be readily appreciated by those familiar with the varying ductile qualities of metals used in the manufacturing of screws, that the design of the tool for swaging the ta r end may be varied consider.-

ably to e ect the swaging of some metals and some sizes of screws to a more or less sharp point while other metals and sizes may be formed with only a tapered or chamfered edge. The designing of the swaging tool may extend over a wide range of bevels in accordance with requirements.

The invention does not necessitate the provision of special thread rolling dies. Standard dies are used and by merely forming the slot 3 therein in the required position in any suitable manner the point forming tool may be placed therein and the new invention is complete. It will be noted that a recess 11 is formed between the end 7 of the swaging tool and the bottom of the slot 3. This is provided so that the tool may be readily removed for replacement when desired.

The extreme simplicity of this invention will be readily apparent and it will be a preciated that the ordinary operation 0? the standard thread rolling machine is not altered in an way, consequently it must be understood t at no extra cost in the operation of making a pointed screw is involved over the making of a square ended screw and as the article is greatly enhanced a very depushes same downward to form areduced extension.

2. Means for roll threading and pointing screws comprising a pair of thread forming dies, movable one in relation to the other to roll a blank therebetween, a tool inserted in one of said dies at the bottom of the thread forming portion, said tool having a ridge of angular cross section arranged longitudinally in diverging relation to the said bottom of the thread forming portion of the die whereby the said ridge retreats progressively downward relative to the blank to gather and push the metal at the lower end thereof into a reduced extension formation.

3. Means for roll-threading and pointing screws comprising a pair of thread forming dies movable one in relation to the other to roll a blank therebetween, a tool removably inserted in one of said dies at the bottom limit of the thread forming portion, said tool having its outer side formed with a ridge comprising two sides meeting at a sharp angle, said ridge extending diagonally to the .plane of the working surface of the die whereby it approaches closer to the blank axis as the blank is advanced and also sloping downwardly in the direction of advance of the blank, whereby the said ridge engages the metal at the bottom ends of the blank at a depth and at a distance from the said bottom limit of the thread forming portion which increases progressively in proportion to the advance, of the blank between said dies, to gather and push the said metal into a tapered extension formation.

4. Means for roll threading and pointing screws comprising a pair of thread forming dies movable one in relation to the other to roll a blank therebetween, a swcdging ridge carried by one of said dies, said ridge being disposed in diagonal relation to the path of movement of the movable dies and engaging the metal at the bottom of the blank as it is rolled between the dies whereby said ridge gathers the said metal and pushes same downwardly to form a reduced extension, means being provided for rogressively rolling the reduced extension ormed by said gathered metal and producing a smooth surface thereon.

5. Means for roll threading and pointing screws comprising a pair of thread forming dies movable one in relation to the other to roll a blank therebetween, a swedging ridge carried by one of said dies, said rldge bein 5 disposed in diagonal relation to the path movement of the movable die and being of progressively increasing hei ht above the working face of the die an engaging the metal at the bottom of the blank as it is rolled [0 between the dies, whereby said ridge gathers the said metal and pushes same downwardly and inwardly toward the blank axis to form a reduced tapered extension.

6. Means for roll threading and pointing 1 screws comprising a pair of thread forming dies movable one in relation to the other to roll a blank therebetween, a swedging ridge carried by one of said dies, said ridge being disposed in diagonal relation to the path of movement of the movable die and being of progressively increasing height above the wor ing face of the die and engaging the metal at the bottom of the blank as it is rolled between the dies, whereby said ridge gathers the said metal and pushes same downwardly and inwardly toward the blank axis to form a reduced tapered extension, means being provided for effecting a final surface rolling of the reduced ta ered extension formed by said gathered meta to produce a smooth tapered surface thereon.

7. Means for roll threading and pointing screws as claimed in claim 3 in which the disposition and downward slo e of said ridge is such in relation to the blan and die members that it clears the extreme end of the tared extension at a point intermediate of the length of travel of the blank with the ad- 'acent side of said ridge maintaining a roll- 40 mg surfacing contact with the said tapered extension.

8. Means for roll threading and pointin screws as claimed in claim 2 in which sai tool is inserted in a bottomed slot in the die member and a recess. is formed between the end of the tool and the slot bottom to permit insertion of anvimplement to pry the tool from the slot when it is desired to remove same. 0- PETER L. ROBERTSON. 

